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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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474                                ALASKAN GLACIER STUDIES
ton and Hoodoo Islands arise to heights of from 1000 to 1967 feet, and Flemming Island is still higher.
None of these islands have glaciers. Grant and Higgins statel that the Prince William Sound Glacier extended nearly or quite to their summits, reaching about 2000 feet on the border of Port Bainbridge, and extending out past the end of Eirington Island, the southwesternmost island of Prince William Sound. This western distributary of the Prince William Sound Glacier, therefore, ended in the open Pacific Ocean.
We have not seen these islands except from a steamer in Eirington and Latouche Passages in 1904 and 1911, and from a launch in Knight Island Passage and eastern Latouche Passage in 1910; but the steep lower slopes give an impression of intense glacia-tion, being most abrupt on the southeastern side, as on Latouche Island.
These steep slopes are continued below sea level, as the Coast Survey charts show.2 These fiords all follow the strike of the rocks and are all rather simple in outline, and flat-bottomed. The depth of Bainbridge and Prince of Wales Passages is unknown, except in the southwestern end of the latter where it reaches 504 to 606 feet. This contrasts with a maximum of 234 to 842 feet in the southwestern end of Eirington Passage, which is tributary to lower Prince of Wales Passage. The descent of 260 to 270 feet in a half mile of the fiord bottom suggests a submerged hanging valley relationship. This would be a natural result of greater glacial erosion in the broader Prince of Wales Passage, which leads straight from Knight Island Passage, and which doubtless had a more effective ice stream than the narrower, crooked Elrington Passage.
Within Eirington Passage there seems to have been differential glacial erosion, for this fiord, which has a right-angled turn near the southern end, reaches its greatest depth in a basin 594 feet deep, just at the elbow- This is an increase of depth amounting to 246 feet in a mile and a quarter, measured from the northeast, and 294 feet in five-eighths of a mile, measured from the northwest, and suggests that the ice tongue of Eirington Passage eroded this deeper rock basin because its free movement was retarded at this sharp turn.
Latouche Passage has two rather different parts. From Ellington Passage northeastward the depths vary from 480 to 750 feet, contrasting with the southwestern half, which is from 60 to 264 feet deep. This contrast suggests the possibility that before and after the main period of glaciation, when the ice probably streamed southwestward through Latouche Passage, the local glaciers from the great cirques of Latouche Island, most of which face the deep northeastern hah7 of the fiord, extended out into the passage and supplied an ice stream which moved toward the northeast rather than the southwest, therefore eroding the broader northeastern part of the fiord most deeply.
There are submerged barriers on the bottom at both ends of Latouche Passage, the one facing the Pacific Ocean, near Danger Island, having a roughly-crescentic shape, with depths of from SJ to 60 feet, in contrast with 264 feet just inside and 150 feet an equal distance outside. Two narrow channels with depths of 78 and 84 feet respectively cross this obstruction, which curves both ways from the low Danger Island. The shallow mouth of this fiord, contrasting with the deep, open termini of the wider Prince of Wales Passage and Montague Strait may be due either to lack of glacial erosion here or to the deposition of a terminal moraine below sea level.
> Bull. 448, U. S. Geol, Survey, 1010, p. 10.
* U. S. Coast and Geod. Survey, Charts 8522 and 8515.